1. Field of the Invention
The present invention relates to a combustion process using separate injections of at least one fuel and of at least one oxidizer, as well as to the use of this process for controlling and/or regulating the position of a flame when separate injections of the said fuels and oxidizers are used.
2. Description of the Related Art
The combustion process is carried out in a furnace comprising a floor on which a charge to be heated is placed, and a roof lying above the charge, into which a first fluid and a second fluid are injected separately, these fluids being capable of causing combustion between them, the injections of these fluids being carried out between the surface of the charge and the roof, the first fluid being either a combustible fluid or an oxidizer fluid, whereas the second fluid is either an oxidizer fluid or a combustible fluid.
Many documents in the prior art, such as U.S. Pat. Nos. 4,863,371, 4,946,382, 4,988,285 and U.S. Pat. No. 5,076,779, describe methods for the combustion of a fuel using an oxidizer such as oxygen or oxygen-enriched air, in which the amount of nitrogen oxides (NO.sub.x) generated is reduced.
Other publications, for example such as U.S. Pat. Nos. 4,541,796, 5,302,112 and U.S. Pat. No. 5,643,348, describe burners having different geometries, corresponding especially to separate injections of fuels and of oxidizers, the differences between these burners essentially consisting of the number of injections or of injectors, the distance between the injectors, their relative positions, etc.
These various processes, as well as the use of these various burners in a furnace in which a charge has to be heated or melted by the supply of energy from these burners, all have, however, the drawback that, when the burners are fitted or when it is desired to carry out the said processes, it may happen that the separate injections of fuels and of oxidizers, more particularly when the fuel is injected above the oxidizer, tend to cause the fuel to rise towards the roof, thereby causing combustion, i.e. a hot flame, near the roof. Such an operation may be particularly dangerous, since it may destroy the roof of the furnace.
At the present time, the problem therefore arises, when separate injections of fuels and of oxidizers are used, of how to control these injections so as to prevent the fuel/oxidizer mixture, and preferably at least the fuel, from rising towards the roof. The purpose of this control is to keep the gases more or less in the region of the height at which they are injected into the furnace, without these oxidizers and/or fuels undergoing a substantial rise towards the roof. The expression "substantial rise" should be understood to mean a rise which would bring gases whose temperature is too high and/or gases that are reducing (or that are too reducing) in the region of the roof, something which, in both cases, could result in the refractories in the roof being damaged.